Polyorganosiloxane elastomers, such as polydimethylsiloxane-based elastomers, are frequently used in the electronics industry for properties such as their thermal stability and ability to relieve stresses over a broad thermal range. However, these polyorganosiloxane elastomers may suffer from the drawback of poor resistance to some organic chemicals, such as solvents and engine oils.
Fluorosilicone elastomers and organic elastomers have been used to improve chemical resistance. However, fluorosilicone elastomers suffer from the drawback of having higher cost than polyorganosiloxane elastomers (that are non-fluorinated). One proposed approach to address this is to combine fluorosilicone elastomers with polyorganosiloxane elastomers. However, proposed approach has generally not been used due to concerns that the fluorosilicone and non-fluorinated organosilicone components would phase separate, resulting in unstable properties.
Silicone compositions that cure to form elastomers may also suffer from the drawback of poor resistance to Bleed. Bleed can be problematic in applications in which the composition is applied to a portion of a substrate before curing. The species that Bleed (out of the silicone composition) may contaminate the substrate. This tends to be particularly problematic for adhesives, such as die attach adhesives used in electronics applications, because the addition of adhesion promoters to hydrosilylation-reaction curable polyorganosiloxane elastomer compositions has been found to increase Bleed.
Organic elastomers may suffer from the drawback of having insufficient flexibility or bulk thermal properties. Therefore, there is a need in the electronics industry for curable silicone compositions having improved resistance to Bleed, where the curable silicone compositions cure to form elastomers having improved chemical resistance and resistance to Bleed, while retaining flexibility and bulk thermal properties.